Multiple-port, multiple-chamber, tuned air-powered subsea seismic source

Abstract

The invention is a multi-port, multi-chamber, tuned, air-powered subsea seismic source. It is suitable for producing a seismic wave in a subsea environment during seismic prospecting. Interconnected pressurized chambers are formed between plates located on a movable shuttle and cylinder walls extending inward from the source housing. The source is fired by moving the shuttle through a stroke and allowing the pressurized air within the air chambers to exit through ports into the surrounding water. A unique seal arrangement in also shown.

I claim as my invention: 
     
       1. A seismic cource suitable for producing a seismic wave in a liquid, said seismic source comprising: (a) a housing having a generally tubular body, two longitudinal ends, and a longitudinal axis, said tubular body having an inner side;   (b) a plurality of cylinder walls extending inwardly from said inner side of said tubular body, said cylinder walls being axially spaced along said longitudinal axis between said longitudinal ends so as to define a plurality of longitudinally spaced chambers in said housing, said chambers comprising, alternatively, pressure chambers and port chambers such that each port chamber is located between two pressure chambers, each of said cylinder walls having a port chamber side, a pressure chamber side, and a central bore therethough, said central bore being substantially co-axial with said longitudinal axis;   (c) a shuttle disposed within said housing, said shuttle being axially movable through a stroke and comprising, (i) a shuttle shaft passing loosely through said central bore in each of said cylinder walls so as to define an annular passageway around said shuttle shaft in each of said cylinder walls, said shuttle shaft having an axis substantially coincident with said longitudinal axis and two ends, each of said ends being supported by said housing, and   (ii) a plurality of longitudinally spaced shuttle plates mounted on said shuttle shaft, each of said shuttle plates corresponding to and being located in one of said longitudinally spaced chambers in said housing, said shuttle plates being adapted to seal each of said pressure chambers only at each end of said storke;     (d) one or more ports communicating through said tubular body and into each of said port chambers;   (e) means for supplying pressurized air to said pressure chambers; and   (f) means for moving said shuttle axially through said stroke; whereby pressurized air in each of said pressure chambers exits through said annular passageways into said port chambers and thence through said ports to produce a seismic pulse in said liquid when said shuttle is moved through said stroke.     
     
     
       2. The seismic source of claim 1 wherein said housing includes an accumulator chamber at each of said longitudinal ends, said accumulator chambers being located, respectively, beyond said ends of said shuttle shaft, each of said accumulator chambers being in communication with at least one of said pressure chambers. 
     
     
       3. The seismic source of claim 2 wherein each of said longitudinal ends of said housing includes a generally cylindrical actuation chamber substantially co-axial with said longitudinal axis, said actuation chamber being in communication with said accumulator chamber, and wherein each of said ends of said shuttle shaft has a pressure surface formed thereon and extends, respectively, into one of said actuation chambers, whereby pressurized air in said accumulator chamber flows into said actuation chamber and presses on said pressure surface to urge said shuttle through said stroke. 
     
     
       4. The seismic source of claim 1 wherein each of said cylinder walls includes, (a) a first seal and a second seal mounted in said port chamber side of said cylinder wall so as to circumscribe said central bore, said first seal having a diameter larger than the diameter of said second seal,   (b) a third seal mounted in said pressure chamber side of said cylinder wall so as to circumscribe said central bore, said third seal having a diameter larger than the diameter of said second seal and smaller than the diameter of said first seal, and   (c) means for introducing pressurized air between said first seal and said second seal, said second and third seals cooperating with said shuttle plates to seal each of said pressure chambers at each end of said stroke, and wherein movement of said shuttle through said stroke is initiated by introducing pressurized air between said first and second seals in each of said cylinder walls.     
     
     
       5. The seismic source of claim 4 wherein each of said first, second, and third seals has a back face and a sealing face adapted to sealingly contact one of said shuttle plates at one end of said stroke, and wherein said seismic source further comprises means for extending said seals outwardly from said cylinder walls. 
     
     
       6. The seismic source of claim 5 wherein said means for extending said seals comprises passageways formed in said cylinder walls for supplying pressurized air from said pressure chambers to said back face of each said seal. 
     
     
       7. The seismic source of claim 5 wherein said means for extending said seals comprises one or more springs adapted to press outwardly on said back face of each said seal.